1. Field of the Invention
This invention relates to a syringe and in particular to a plastic syringe suitable for use as a pre-filled product.
2. Description of the Related Art
In recent years, there have been significant shifts in medical practice due to an increasing awareness of the risks of transfer of various transmissible viruses such as AIDS--HIV and hepatitis especially when treating a number of patients. In particular, medical practitioners are increasingly alert to the risks of virus transfer associated with the re-use of surgical and other medical apparatus. For this and other reasons, there are stronger calls for reliable and easy to use medical and surgical appliances which are disposable after a single use. This is particularly so when it comes to hypodermic syringes. As hypodermic needles come into contact with bodily fluids there is a risk of cross infection if the same syringe is used more than once--even if the actual hypodermic is disposed of after each use. Pre-filled disposable syringes are in demand for these and other reasons. A single dose product already accurately filled and labelled with the name of the injectable is convenient and moreover safer to use as there is lower risk of incorrect dosing on administration. It is used once and discarded. There is no need to re-sterilize the equipment and there is no need to carefully transfer the injectable from a separate ampoule.
An example of a pre-filled syringe is described in the Applicant's Australian patent 595096. The syringe described in that patent is sealed at one end by al stopper and at the other by a closure which is integral with the syringe. The closure is adapted to be removed so that after removal a hypodermic needle may be fitted to the end of the syringe for injection of the contents. The closure is described as being removable by twisting with an appropriate shaped tool or by snap action.
A further example of a pre-filled syringe is described in the Applicant's Australian patent 635631 wherein the syringe described is also fitted with an integral closure. The closure is adapted to be broken from the end of the syringe on the application of a hypodermic needle onto the needle fitting on the syringe. The closure is moved into the syringe and retained within a chamber at the needle end of the syringe.
Whilst both of the aforementioned products represented significant improvements over other prior pre-filled syringes, the present invention relates to a variation in syringe design which brings with it certain advantages (in some applications) over both of the previously described products which will be apparent from the following more detailed discussion.